B737 Max : CAA bans from UK airspace; Comair aircraft grounded
Mar 14, 2019, 7:51 am
#211
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I refer back to my original post, I guess that you were just throwing in a bit of lightheartedness as yes I don’t profess to be an engineer, or be any expert at all but as per this snippet in today’s Times I don’t think I was completely off the ball on what I was attempting to understand about MCAS, engine placement etc. See attached. Then again this is the news, what do they know?!
If you weren’t joking and simply being a bit disrespectful to a generally interesting conversation then I would also suggest to stop reading the thread.
It's actually the opposite... because of the more powerful engines, the nose will tend to pitch up more and can get out of control if the pilot isn't on his game. MCAS pushes the nose back down.
Mar 14, 2019, 9:26 am
#212
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On Aviaton Herald they have the report on the Lion Air crash.
this paragraph may or may not be relavent:
For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.
...
The FAA says it anticipates mandating this software enhancement with an Airworthiness Directive (AD) no later than April. We have worked with the FAA in development of this software enhancement.
It is important to note that the FAA is not mandating any further action at this time, and the required actions in AD2018-23.5 continue to be appropriate.
this paragraph may or may not be relavent:
For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.
...
The FAA says it anticipates mandating this software enhancement with an Airworthiness Directive (AD) no later than April. We have worked with the FAA in development of this software enhancement.
It is important to note that the FAA is not mandating any further action at this time, and the required actions in AD2018-23.5 continue to be appropriate.
How long to get the 737Max back in service would depend on certification of changes to the aircraft.
The fact that Boeing has been working on this for "several months" suggests that the grounding will last for only a few weeks to months rather than the 6-9 months that I had anticipated initially:
1. New software for MCAS
2. Fly new MCAS software certain number of hours and flight modes to convince FAA that it fixes problem and does not create new ones.
1 and 2 are probably done saving 2-4 months time.
3. Training for 737Max flight crews in new MCAS software is limited by the number of Max simulators available (differs from standard 737 simulator). This not something you would want to do in the aircraft itself
.4. Total time to roll out software and verify its intact in the aircraft and verify crew training: at least 6 weeks to 6 months.
Mar 14, 2019, 9:29 am
#213
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This is one of the clearest explanations (to me, at least) of what this MCAS is all about ...
https://www.pprune.org/10418385-post1356.html
https://www.pprune.org/10418385-post1356.html
Mar 14, 2019, 10:19 am
#214
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https://www.nytimes.com/interactive/...gtype=Homepage
Should be available for free access if you haven't read too many nytimes.com articles this month.
The summary is that tracking data from Aireon (Satellite-based ADS-B tracking) shows a similar profile in vertical speed and the period of oscillations to the Lion Air incident. The period is important because it suggests that MCAS was involved.
Mar 14, 2019, 10:23 am
#215
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The New York Times has an article on what might be the reason the Canadian TSB went with the grounding:
https://www.nytimes.com/interactive/...gtype=Homepage
Should be available for free access if you haven't read too many nytimes.com articles this month.
The summary is that tracking data from Aireon (Satellite-based ADS-B tracking) shows a similar profile in vertical speed and the period of oscillations to the Lion Air incident. The period is important because it suggests that MCAS was involved.
https://www.nytimes.com/interactive/...gtype=Homepage
Should be available for free access if you haven't read too many nytimes.com articles this month.
The summary is that tracking data from Aireon (Satellite-based ADS-B tracking) shows a similar profile in vertical speed and the period of oscillations to the Lion Air incident. The period is important because it suggests that MCAS was involved.
Mar 14, 2019, 10:51 am
#216
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This is one of the clearest explanations (to me, at least) of what this MCAS is all about ...
https://www.pprune.org/10418385-post1356.html
https://www.pprune.org/10418385-post1356.html
My concern with reading the articles is the reason for MCAS in the first place, and the way it's been implemented. Globaliser gave a helpful response in another thread regarding the 777x, where I asked if MCAS was also used on there.
AIUI, MCAS is an electronic system grafted on to a traditional cable-and-pulley aircraft. In contrast, the 777 has been fly-by-wire since day 1. I'm not an expert, but on the face of it, it seems unlikely that any adjustments to the 777X that are thought desirable would be done by grafting on a separate system.
Am I alone in thinking that "Manoeuvring Characteristics Augmentation System" is a rather euphemistic description? From my reading it's an electronic system installed inline to the traditional manual flight controls that compensates for the differences between the previous 737's and the Max in order to achieve the all important same type certification that airlines require to avoid costly retraining etc. It sounds awfully like a short sighted fudge, when the alternatives would have taken longer to develop and less economically and practically desirable to customers.
The implementation seems basically, and politely, a 'bodge', that may well be the primary cause of the deaths of over 300 people.
Realise the above may be inflammatory so happy to be corrected.
Mar 14, 2019, 10:58 am
#217
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Without getting technical beyond my abilities or knowledge, I tend to agree.
Making MAX certifiable, via the grandfathered rights of 50 years of 737s, seemed to require this ‘fudge’ to get through. Whether this was a crass error will undoubtedly be revealed when both investigations are completed, Certainly I will avoid flying in a MAX until matters are clarified/resolved.
Making MAX certifiable, via the grandfathered rights of 50 years of 737s, seemed to require this ‘fudge’ to get through. Whether this was a crass error will undoubtedly be revealed when both investigations are completed, Certainly I will avoid flying in a MAX until matters are clarified/resolved.
Mar 14, 2019, 12:21 pm
#219
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I just read that the black boxes (normally they are orange though ) have been sent to Paris for investigation - curious as to why Paris? Would have thought they would go to somewhere completely 100% independent? Of course where safety is concerned, national interest and politics absolutely should not come into play but.....
) have been sent to Paris for investigation - curious as to why Paris? Would have thought they would go to somewhere completely 100% independent? Of course where safety is concerned, national interest and politics absolutely should not come into play but.....
Mar 14, 2019, 12:30 pm
#220
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The evidence they've found on the site is either the black boxes or something else. The jackscrew on the stabilisers would be the prime suspect as it would give an indication of what the trim was doing.
The problem that Boeing has got with MCAS is that while it's easy to say 'turn it off if the AoA sensors disagree', the original risk case for which it was designed still exists, and that action would compromise it. As type certification is hanging off this subsystem, they have to think of something that works in all cases.
It seems odd to create a fix that fix that makes it progressively less easy to handle as an incident unfolds. In the worst case you need two pilots pulling back hard on their yokes, trying to turn the trim wheel, and pulling a circuit breaker, while the altimeter is windmilling.
I said I thought panic is a possible factor, by that I don't mean hands in the air and screaming, but a reduction of capacity to deal with a situation due to the unexpected event, sensory overload, and disorientation. That may not have been anticipated in the design, but let's see. The pilots may have thought they were dealing with another problem entirely, loss of thrust or faulty airspeed indication.
The problem that Boeing has got with MCAS is that while it's easy to say 'turn it off if the AoA sensors disagree', the original risk case for which it was designed still exists, and that action would compromise it. As type certification is hanging off this subsystem, they have to think of something that works in all cases.
It seems odd to create a fix that fix that makes it progressively less easy to handle as an incident unfolds. In the worst case you need two pilots pulling back hard on their yokes, trying to turn the trim wheel, and pulling a circuit breaker, while the altimeter is windmilling.
I said I thought panic is a possible factor, by that I don't mean hands in the air and screaming, but a reduction of capacity to deal with a situation due to the unexpected event, sensory overload, and disorientation. That may not have been anticipated in the design, but let's see. The pilots may have thought they were dealing with another problem entirely, loss of thrust or faulty airspeed indication.
Mar 14, 2019, 12:34 pm
#221
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Without getting technical beyond my abilities or knowledge, I tend to agree.
Making MAX certifiable, via the grandfathered rights of 50 years of 737s, seemed to require this ‘fudge’ to get through. Whether this was a crass error will undoubtedly be revealed when both investigations are completed, Certainly I will avoid flying in a MAX until matters are clarified/resolved.
Making MAX certifiable, via the grandfathered rights of 50 years of 737s, seemed to require this ‘fudge’ to get through. Whether this was a crass error will undoubtedly be revealed when both investigations are completed, Certainly I will avoid flying in a MAX until matters are clarified/resolved.
It is clear some of the characteristics of the older systems become detrimental as the original 1960s design is stretched, tweaked again and again, then further modified with bolt-on modern systems to preserve the grandfather rights (to reduce certification costs) and for the all important common type rating with previous generation 737. I wonder if this incident will hasten Boeing to go for the all new single-aisle design they have been mooting for yeard - it now seems really long overdue.
As I posted earlier up-thread, Boeing seems to have lost some (some may say alot) of it's safety culture as the last two planes launched by the company have had to be grounded worldwide on safety reasons shortly after EIS. IIRC, the last plane grounded for safety reasons in the modern jet era was the DC10 a whopping 40 years ago this year. Having TWO new types grounded in the space of 5-6 years is truly appalling by modern standards.
Last edited by BOH; Mar 14, 2019 at 1:05 pm
Mar 14, 2019, 1:23 pm
#222
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Apart from being an engineer myself, my interest here is due to having made four flights on Max 8s (2 x AC and 2 x AA) all since the Lion Air crash! I am, therefore, quite perturbed that Boeing may have unnecessarily but myself and my family at risk: all to protect shareholder interests over those of passengers. It is quite horrific that further lives had to be lost to get where we are today!
Mar 14, 2019, 1:56 pm
#223
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I just read that the black boxes (normally they are orange though ) have been sent to Paris for investigation - curious as to why Paris? Would have thought they would go to somewhere completely 100% independent? Of course where safety is concerned, national interest and politics absolutely should not come into play but.....
) have been sent to Paris for investigation - curious as to why Paris? Would have thought they would go to somewhere completely 100% independent? Of course where safety is concerned, national interest and politics absolutely should not come into play but.....Still, to me it seems almost negligent that those black boxes were just sitting in Ethiopia for several days instead of being sent somewhere for analysis as soon as they were recovered.
The evidence they've found on the site is either the black boxes or something else. The jackscrew on the stabilisers would be the prime suspect as it would give an indication of what the trim was doing.
The problem that Boeing has got with MCAS is that while it's easy to say 'turn it off if the AoA sensors disagree', the original risk case for which it was designed still exists, and that action would compromise it. As type certification is hanging off this subsystem, they have to think of something that works in all cases.
It seems odd to create a fix that fix that makes it progressively less easy to handle as an incident unfolds. In the worst case you need two pilots pulling back hard on their yokes, trying to turn the trim wheel, and pulling a circuit breaker, while the altimeter is windmilling.
I said I thought panic is a possible factor, by that I don't mean hands in the air and screaming, but a reduction of capacity to deal with a situation due to the unexpected event, sensory overload, and disorientation. That may not have been anticipated in the design, but let's see. The pilots may have thought they were dealing with another problem entirely, loss of thrust or faulty airspeed indication.
The problem that Boeing has got with MCAS is that while it's easy to say 'turn it off if the AoA sensors disagree', the original risk case for which it was designed still exists, and that action would compromise it. As type certification is hanging off this subsystem, they have to think of something that works in all cases.
It seems odd to create a fix that fix that makes it progressively less easy to handle as an incident unfolds. In the worst case you need two pilots pulling back hard on their yokes, trying to turn the trim wheel, and pulling a circuit breaker, while the altimeter is windmilling.
I said I thought panic is a possible factor, by that I don't mean hands in the air and screaming, but a reduction of capacity to deal with a situation due to the unexpected event, sensory overload, and disorientation. That may not have been anticipated in the design, but let's see. The pilots may have thought they were dealing with another problem entirely, loss of thrust or faulty airspeed indication.
Some of your comments go back to the copilot with only 200 hours. He/she couldn't be expected to be very helpful in an emergency situation like this. Even without panic, it would be very important to know instantly what to do and to do it quickly and without hesitation.
Mar 14, 2019, 2:03 pm
#224
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The delay in sending the flight Recorders could be explained by trying to (a) get someone competent/capable to so the data extraction, and (b) getting someone NOT in the USA to do it.
Last edited by T8191; Mar 14, 2019 at 2:13 pm Reason: typo
Mar 14, 2019, 4:32 pm
#225
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I would have thought that the most important thing would have been to ensure that wherever they went, they would be handled properly and all available information accurately extracted. If it takes several days to identify an appropriate location, it takes several days. That is surely more a case of necessary caution rather than negligence. What would have been negligent would have been rushing them somewhere just for the sake of speed, only for that to cause all of the recorder data to be inadvertently destroyed.